Its Manufacture
The present invention relates to electro-optical display elements, particularly liquid-crystal displays and a method for the manufacture thereof, in which an electrically conductive layer is applied to a glass substrate and an insulating layer is then applied on top thereof, the insulating layer being first subjected to a drying process and then to a firing process and then being removed in the region of contacting points of the conductive layer.
As is known, in a large number of electro-optical displays, particularly in the case of nematic, dichroitic or dipole suspension displays, the conductive layers applied to the front or rear glass substrate are covered with an insulating layer in order to prevent the conductive layer from being decomposed by electrolytic processes during the operation of the display element. The manner of procedure here is that, after the application and structuring of the conductive layer, the insulating layer is applied by dipping, whirling or roller-coating. After its application, the insulating layer is subjected at low temperature to a brief drying process and then fired at temperatures of about 400.degree. C. After the conclusion of the firing process, the insulating layer is removed in the region of the contacting points of the conductive layer to which the connections for the control lines are to be subsequently connected, this being done by exposing the contact points by means of scratching or etching. This scratching or etching of the contact points is very time-consuming, with great risk of failure inherent therein. Furthermore, the etching or scratching process can be automated only with considerable difficulties and at high technological expense.
It has also already been proposed not to coat the conductive layers completely with an insulating layer but to leave them free of coating at the contact points. Since the coating of the conductive layers with the insulating substance, for instance silicon oxide, silicon dioxide or else yttrium oxide, is effected by the offset process, extensive re-adjustment of the coating system is necessary for each display, which has a detrimental effect on the flexibility of the manufacture of the display and increases the cost of manufacture. These disadvantages are not present when the layers are applied by the silk-screen process, but such a silk-screen process is very problematical in connection with the insulating layers from a technical standpoint, and for this reason has not been used in mass production up to the present time.